John,
I didn't think anyone would respond...
I have done several, but I doubt I'll ever do another..The amount of machine work is extensive. Very small # 2 & 3 screws are needed to secure the insert. The inserts I made were larger, and resisted loosening..The AA insert is too small, and the two screws just can't support it, even with super loc tite..
There is a sweet spot on each gun that offers reliable consistant lock back, and it's not easy to figure out. If the notch is off by a 10 or 15 thousandths, the gun has failures to lock back..If placed at the location of the factory notch, it will not work. It is a challenge if a smith is so inclined..
One of the very best 22 target pistols available is the Pardini..It does not lock back..Please don't take the wrong way, and I work on a "lot" of Marvels, and, the Marvel is a GREAT conversion, but I wouldn't trade one Pardini for ten Marvels that locked back...
Jerry

I set up a Colt frame -roll trigger, etc for a friend that got a new Marvel U1 lock back, the alumimum one.

I shot it and he shoots bullseye with me every week, he's got about 500 rounds through it.

The GSG mag that came with the unit didn't lock back reliably and had some feeding issues.

I gave him an Advantage Arms magazine that has proven to be flawless in lock back and feeding. Another in the bullseye league just got the same lock back U1, his would'nt work with the GSG mags either but the AA magazines work perfectly.

I was somewhat surprised how they designed the slide on the lock back - instead of a steel insert that catches the slide release they built out the slide as a protrusion of aluminum, part of the slide not a separate piece.

I can't comment on the longevity so far. I did suggest to my friends they sling-shot when releasing the slide rather than dropping the slide release so as not to wear the steel slide release against the aluminum "protrusion".

I can say from experience that Marvel Precision's customer service/warranty is excellent.

I'm impressed with the lock back U1 that I intend on getting one. I've shot a couple of old style U1's for more than 5 years and 4 cases of CCI SV ammo.

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